A decoloring apparatus heats a paper to decolor the color of image printed on the paper. The processing of decoloring the color of image is referred to as a decoloring processing. After the decoloring apparatus carries out the decoloring processing, a scanner scans the paper to determine whether or not there is an image left on the paper to which the decoloring processing is carried out. Then, when there is an image left on the paper, a CPU (Central Processing Unit) determines the paper as a defective paper (that is, the paper that cannot be reused).
A predetermined form may be printed on the paper with non-decolorable toner in advance. The predetermined form may be a frame in a predetermined format, or a predetermined mark. When an image is formed with a decolorable toner on the paper where the predetermined form is printed, the predetermined form still remains even if the decoloring processing is carried out on the paper.
As stated above, when the paper on which the image is left is determined as the defective paper, the paper on which the predetermined form still remains should also be determined as the defective paper. However, if the color of the image of which the color should have been decolored is decolored, the paper on which only the predetermined form remains can be reused and shouldn't be thought as the defective paper.
The purpose of this invention is to provide a decoloring apparatus which can distribute other papers and the paper on which only the predetermined form still remains among the papers to which the decoloring processing is carried out.